Measuring distance in wireless devices

ABSTRACT

Aspects of the present disclosure provide techniques for efficient ranging. According to certain aspects, techniques are provided to signal the use of different resolutions of time units for parameters to be used in a ranging procedure, such as a fine timing measurement (FTM) procedure.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

The present Application is a continuation of U.S. patent applicationSer. No. 15/088,108, filed Mar. 31, 2016, pending, which claims benefitof and priority to U.S. Provisional Patent Application Ser. No.62/167,145, filed May 27, 2015, both of which are assigned to theassignee hereof and hereby expressly incorporated by reference herein intheir entirety.

BACKGROUND Field of the Disclosure

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to efficient ranging and distancemeasurement in wireless devices.

Description of Related Art

Wireless communication networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, etc. These wireless networks may be multiple-access networkscapable of supporting multiple users by sharing the available networkresources. Examples of such multiple-access networks include CodeDivision Multiple Access (CDMA) networks, Time Division Multiple Access(TDMA) networks, Frequency Division Multiple Access (FDMA) networks,Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA)networks.

In order to address the desire for greater coverage and increasedcommunication range, various schemes are being developed. One suchscheme is the sub-1-GHz frequency range (e.g., operating in the 902-928MHz range in the United States) being developed by the Institute ofElectrical and Electronics Engineers (IEEE) 802.11ah task force. Thisdevelopment is driven by the desire to utilize a frequency range thathas greater wireless range than wireless ranges associated withfrequency ranges of other IEEE 802.11 technologies and potentially fewerissues associated with path losses due to obstructions.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications in a wireless network.

Aspects of the present disclosure provide an apparatus for wirelesscommunications. The apparatus generally includes a processing systemconfigured to generate a first frame providing an indication of one ormore resolutions of units of time to use for one or more parameters (atleast one parameter) to be used in a ranging procedure performed with awireless node and a first interface configured to output the first framefor transmission to the wireless node.

Aspects of the present disclosure provide an apparatus for wirelesscommunications. The apparatus generally includes a first interfaceconfigured to obtain a first frame transmitted from a wireless node anda processing system configured to determine, based on an indication inthe first frame (indicating), one or more resolutions of units of timeto use for one or more parameters to be used in a ranging procedureperformed with the wireless node and perform the ranging procedure withthe wireless node according to the determined resolutions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a diagram of an example wireless communicationsnetwork, in accordance with certain aspects of the present disclosure.

FIG. 2 illustrates a block diagram of an example access point and userterminals, in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates a block diagram of an example wireless device, inaccordance with certain aspects of the present disclosure.

FIG. 4 is an example call flow illustrating a frame exchange for a finetiming measurement (FTM) procedure, in accordance with certain aspectsof the present disclosure.

FIG. 5 illustrates a block diagram of example operations for wirelesscommunications by an initiating apparatus (e.g., configured to initiatea ranging procedure), in accordance with certain aspects of the presentdisclosure.

FIG. 5A illustrates example means capable of performing the operationsshown in FIG. 5.

FIG. 6 illustrates a block diagram of example operations for wirelesscommunications by a responding apparatus, in accordance with certainaspects of the present disclosure.

FIG. 6A illustrates example means capable of performing the operationsshown in FIG. 6.

FIGS. 7 and 8 illustrate example resolutions for FTM parameters, inaccordance with certain aspects of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to techniques for measuringdistance based on an exchange of fine timing measurement (FTM) frames ormessages. As used herein, the terms frame and message are usedinterchangeably. According to certain aspects, signaling may be providedthat indicates a resolution for one or more FTM parameters.

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

The techniques described herein may be used for various broadbandwireless communication systems, including communication systems that arebased on an orthogonal multiplexing scheme. Examples of suchcommunication systems include Spatial Division Multiple Access (SDMA)system, Time Division Multiple Access (TDMA) system, OrthogonalFrequency Division Multiple Access (OFDMA) system, and Single-CarrierFrequency Division Multiple Access (SC-FDMA) system. An SDMA system mayutilize sufficiently different directions to simultaneously transmitdata belonging to multiple user terminals. A TDMA system may allowmultiple user terminals to share the same frequency channel by dividingthe transmission signal into different time slots, each time slot beingassigned to different user terminal. An OFDMA system utilizes orthogonalfrequency division multiplexing (OFDM), which is a modulation techniquethat partitions the overall system bandwidth into multiple orthogonalsub-carriers. These sub-carriers may also be called tones, bins, etc.With OFDM, each sub-carrier may be independently modulated with data. AnSC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit onsub-carriers that are distributed across the system bandwidth, localizedFDMA (LFDMA) to transmit on a block of adjacent sub-carriers, orenhanced FDMA (EFDMA) to transmit on multiple blocks of adjacentsub-carriers. In general, modulation symbols are sent in the frequencydomain with OFDM and in the time domain with SC-FDMA.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of wired or wireless apparatuses (e.g.,nodes). In some aspects, a wireless node implemented in accordance withthe teachings herein may comprise an access point or an access terminal.

An access point (“AP”) may comprise, be implemented as, or known as aNode B, Radio Network Controller (“RNC”), evolved Node B (eNB), BaseStation Controller (“BSC”), Base Transceiver Station (“BTS”), BaseStation (“BS”), Transceiver Function (“TF”), Radio Router, RadioTransceiver, Basic Service Set (“BSS”), Extended Service Set (“ESS”),Radio Base Station (“RBS”), or some other terminology.

An access terminal (“AT”) may comprise, be implemented as, or known as asubscriber station, a subscriber unit, a mobile station (MS), a remotestation, a remote terminal, a user terminal (UT), a user agent, a userdevice, user equipment (UE), a user station, or some other terminology.In some implementations, an access terminal may comprise a cellulartelephone, a cordless telephone, a Session Initiation Protocol (“SIP”)phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, a Station (“STA” such as an “AP STA” acting as an AP or a“non-AP STA”) or some other suitable processing device connected to awireless modem. Accordingly, one or more aspects taught herein may beincorporated into a phone (e.g., a cellular phone or smart phone), acomputer (e.g., a laptop), a tablet, a portable communication device, aportable computing device (e.g., a personal data assistant), anentertainment device (e.g., a music or video device, or a satelliteradio), a global positioning system (GPS) device, or any other suitabledevice that is configured to communicate via a wireless or wired medium.In some aspects, the AT may be a wireless node. Such wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as the Internet or a cellular network) via a wired orwireless communication link.

An Example Wireless Communications System

FIG. 1 illustrates a system 100 in which aspects of the disclosure maybe performed. For example, any of the wireless stations including theaccess point 110 and/or the user terminals 120 may be in a neighboraware network (NAN). Wireless stations may exchange fine timingmeasurement (FTM) information for ranging during a period when thewireless stations are already scheduled to wake up (e.g., during apaging window or data window) and may exchange the FTM information usingexisting frames (e.g., association frames, trigger frames and/or/pollingframes, probe request/probe response frames). In aspects, one of thewireless devices may act as a ranging proxy.

The system 100 may be, for example, a multiple-access multiple-inputmultiple-output (MIMO) system 100 with access points and user terminals.For simplicity, only one access point 110 is shown in FIG. 1. An accesspoint is generally a fixed station that communicates with the userterminals and may also be referred to as a base station or some otherterminology. A user terminal may be fixed or mobile and may also bereferred to as a mobile station, a wireless device, or some otherterminology. Access point 110 may communicate with one or more userterminals 120 at any given moment on the downlink and uplink. Thedownlink (i.e., forward link) is the communication link from the accesspoint to the user terminals, and the uplink (i.e., reverse link) is thecommunication link from the user terminals to the access point. A userterminal may also communicate peer-to-peer with another user terminal.

A system controller 130 may provide coordination and control for theseAPs and/or other systems. The APs may be managed by the systemcontroller 130, for example, which may handle adjustments to radiofrequency power, channels, authentication, and security. The systemcontroller 130 may communicate with the APs via a backhaul. The APs mayalso communicate with one another, e.g., directly or indirectly via awireless or wireline backhaul.

While portions of the following disclosure will describe user terminals120 capable of communicating via Spatial Division Multiple Access(SDMA), for certain aspects, the user terminals 120 may also includesome user terminals that do not support SDMA. Thus, for such aspects, anAP 110 may be configured to communicate with both SDMA and non-SDMA userterminals. This approach may conveniently allow older versions of userterminals (“legacy” stations) to remain deployed in an enterprise,extending their useful lifetime, while allowing newer SDMA userterminals to be introduced as deemed appropriate.

The system 100 employs multiple transmit and multiple receive antennasfor data transmission on the downlink and uplink. The access point 110is equipped with N_(ap) antennas and represents the multiple-input (MI)for downlink transmissions and the multiple-output (MO) for uplinktransmissions. A set of K selected user terminals 120 collectivelyrepresents the multiple-output for downlink transmissions and themultiple-input for uplink transmissions. For pure SDMA, it is desired tohave N_(ap)≥K≥1 if the data symbol streams for the K user terminals arenot multiplexed in code, frequency or time by some means. K may begreater than N_(ap) if the data symbol streams can be multiplexed usingTDMA technique, different code channels with CDMA, disjoint sets ofsubbands with OFDM, and so on. Each selected user terminal transmitsuser-specific data to and/or receives user-specific data from the accesspoint. In general, each selected user terminal may be equipped with oneor multiple antennas (i.e., N_(ut)≥1). The K selected user terminals canhave the same or different number of antennas.

The system 100 may be a time division duplex (TDD) system or a frequencydivision duplex (FDD) system. For a TDD system, the downlink and uplinkshare the same frequency band. For an FDD system, the downlink anduplink use different frequency bands. MIMO system 100 may also utilize asingle carrier or multiple carriers for transmission. Each user terminalmay be equipped with a single antenna (e.g., in order to keep costsdown) or multiple antennas (e.g., where the additional cost can besupported). The system 100 may also be a TDMA system if the userterminals 120 share the same frequency channel by dividingtransmission/reception into different time slots, each time slot beingassigned to different user terminal 120.

FIG. 2 illustrates example components of the AP 110 and UT 120illustrated in FIG. 1, which may be used to implement aspects of thepresent disclosure. One or more components of the AP 110 and UT 120 maybe used to practice aspects of the present disclosure. For example,antenna 224, Tx/Rx 222, and/or processors 210, 220, 240, 242, of the AP110, and/or controller 230 or antenna 252, Tx/Rx 254, processors 260,270, 288, and 290, and/or controller 280 of UT 120 may be used toperform the operations 700 and 700A described herein and illustratedwith reference to FIGS. 7 and 7A, respectively, and operations 900 and900A described herein and illustrated with reference to FIGS. 9 and 9A,respectively.

FIG. 2 illustrates a block diagram of access point 110 two userterminals 120 m and 120 x in a MIMO system 100. The access point 110 isequipped with N_(t) antennas 224 a through 224 ap. User terminal 120 mis equipped with N_(ut,m) antennas 252 ma through 252 mu, and userterminal 120 x is equipped with N _(ut,x) antennas 252 xa through 252xu. The access point 110 is a transmitting entity for the downlink and areceiving entity for the uplink. Each user terminal 120 is atransmitting entity for the uplink and a receiving entity for thedownlink. As used herein, a “transmitting entity” is an independentlyoperated apparatus or device capable of transmitting data via a wirelesschannel, and a “receiving entity” is an independently operated apparatusor device capable of receiving data via a wireless channel. In thefollowing description, the subscript “dn” denotes the downlink, thesubscript “up” denotes the uplink, N_(up) user terminals are selectedfor simultaneous transmission on the uplink, N_(dn) user terminals areselected for simultaneous transmission on the downlink, N_(up) may ormay not be equal to N_(dn), and N_(up) and N_(dn) may be static valuesor can change for each scheduling interval. The beam-steering or someother spatial processing technique may be used at the access point anduser terminal.

On the uplink, at each user terminal 120 selected for uplinktransmission, a transmit (TX) data processor 288 receives traffic datafrom a data source 286 and control data from a controller 280. Thecontroller 280 may be coupled with a memory 282. TX data processor 288processes (e.g., encodes, interleaves, and modulates) the traffic datafor the user terminal based on the coding and modulation schemesassociated with the rate selected for the user terminal and provides adata symbol stream. A TX spatial processor 290 performs spatialprocessing on the data symbol stream and provides N_(ut,m) transmitsymbol streams for the N_(ut,m) antennas. Each transmitter unit (TMTR)254 receives and processes (e.g., converts to analog, amplifies,filters, and frequency upconverts) a respective transmit symbol streamto generate an uplink signal. N_(ut,m) transmitter units 254 provideN_(ut,m) the generated uplink signals for transmission from N_(ut,m)antennas 252 to the access point.

N_(up) user terminals may be scheduled for simultaneous transmission onthe uplink. Each of these user terminals performs spatial processing onits data symbol stream and transmits its set of transmit symbol streamson the uplink to the access point.

At access point 110, N_(ap) antennas 224 a through 224 ap receive theuplink signals from all N_(up) user terminals transmitting on theuplink. Each antenna 224 provides a received signal to a respectivereceiver unit (RCVR) 222. Each receiver unit 222 performs processingcomplementary to that performed by transmitter unit 254 and provides areceived symbol stream. An RX spatial processor 240 performs receiverspatial processing on the N_(ap) received symbol streams from N_(ap)receiver units 222 and provides N_(up) recovered uplink data symbolstreams. The receiver spatial processing is performed in accordance withthe channel correlation matrix inversion (CCMI), minimum mean squareerror (MMSE), soft interference cancellation (SIC), or some othertechnique. Each recovered uplink data symbol stream is an estimate of adata symbol stream transmitted by a respective user terminal. An RX dataprocessor 242 processes (e.g., demodulates, deinterleaves, and decodes)each recovered uplink data symbol stream in accordance with the rateused for that stream to obtain decoded data. The decoded data for eachuser terminal may be provided to a data sink 244 for storage and/or acontroller 230 for further processing. The controller 230 may be coupledwith a memory 232.

On the downlink, at access point 110, a TX data processor 210 receivestraffic data from a data source 208 for N_(dn) user terminals scheduledfor downlink transmission, control data from a controller 230, andpossibly other data from a scheduler 234. The various types of data maybe sent on different transport channels. TX data processor 210 processes(e.g., encodes, interleaves, and modulates) the traffic data for eachuser terminal based on the rate selected for that user terminal. TX dataprocessor 210 provides N_(dn) downlink data symbol streams for theN_(dn) user terminals. A TX spatial processor 220 performs spatialprocessing (such as a precoding or beamforming, as described in thepresent disclosure) on the N_(dn) downlink data symbol streams, andprovides N_(ap) transmit symbol streams for the N_(ap) antennas. Eachtransmitter unit 222 receives and processes a respective transmit symbolstream to generate a downlink signal. N_(ap) transmitter units 222providing N_(ap) downlink signals for transmission from N_(ap) antennas224 to the user terminals. The decoded data for each user terminal maybe provided to a data sink 272 for storage and/or a controller 280 forfurther processing.

At each user terminal 120, N_(ut,m) antennas 252 receive the N_(ap)downlink signals from access point 110. Each receiver unit 254 processesa received signal from an associated antenna 252 and provides a receivedsymbol stream. An RX spatial processor 260 performs receiver spatialprocessing on N_(ut,m) received symbol streams from N_(ut,m) receiverunits 254 and provides a recovered downlink data symbol stream for theuser terminal. The receiver spatial processing is performed inaccordance with the CCMI, MMSE or some other technique. An RX dataprocessor 270 processes (e.g., demodulates, deinterleaves and decodes)the recovered downlink data symbol stream to obtain decoded data for theuser terminal.

At each user terminal 120, a channel estimator 278 estimates thedownlink channel response and provides downlink channel estimates, whichmay include channel gain estimates, SNR estimates, noise variance and soon. Similarly, at access point 110, a channel estimator 228 estimatesthe uplink channel response and provides uplink channel estimates.Controller 280 for each user terminal typically derives the spatialfilter matrix for the user terminal based on the downlink channelresponse matrix H_(dn,m) for that user terminal. Controller 230 derivesthe spatial filter matrix for the access point based on the effectiveuplink channel response matrix H_(up,eff). Controller 280 for each userterminal may send feedback information (e.g., the downlink and/or uplinkeigenvectors, eigenvalues, SNR estimates, and so on) to the accesspoint. Controllers 230 and 280 also control the operation of variousprocessing units at access point 110 and user terminal 120,respectively.

FIG. 3 illustrates various components that may be utilized in a wirelessdevice 302 that may be employed within the MIMO system 100. The wirelessdevice 302 is an example of a device that may be configured to implementthe various methods described herein. For example, the wireless devicemay implement operations 700 and 900 illustrated in FIGS. 7 and 9,respectively. The wireless device 302 may be an access point 110 or auser terminal 120.

The wireless device 302 may include a processor 304 which controlsoperation of the wireless device 302. The processor 304 may also bereferred to as a central processing unit (CPU). Memory 306, which mayinclude both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processor 304. A portion of thememory 306 may also include non-volatile random access memory (NVRAM).The processor 304 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 306. Theinstructions in the memory 306 may be executable to implement themethods described herein.

The wireless device 302 may also include a housing 308 that may includea transmitter 310 and a receiver 312 to allow transmission and receptionof data between the wireless device 302 and a remote node. Thetransmitter 310 and receiver 312 may be combined into a transceiver 314.A single or a plurality of transmit antennas 316 may be attached to thehousing 308 and electrically coupled to the transceiver 314. Thewireless device 302 may also include (not shown) multiple transmitters,multiple receivers, and multiple transceivers.

The wireless device 302 may also include a signal detector 318 that maybe used in an effort to detect and quantify the level of signalsreceived by the transceiver 314. The signal detector 318 may detect suchsignals as total energy, energy per subcarrier per symbol, powerspectral density and other signals. The wireless device 302 may alsoinclude a digital signal processor (DSP) 320 for use in processingsignals.

The various components of the wireless device 302 may be coupledtogether by a bus system 322, which may include a power bus, a controlsignal bus, and a status signal bus in addition to a data bus.

Example Ranging/Distance Measurement with FTM

Aspects of the present disclosure provide mechanisms for signaling theuse of different resolutions for units of time of different parametersused in procedures involving wireless stations. For example, themechanism may allow for the use of different resolutions for certainparameters in a ranging procedure, such as a fine timing measurement(FTM) ranging procedure. The ability to signal different resolutions mayallow more accurate timing measurements in certain cases, which may leadto more accurate distance measurements.

Fine timing measurement (FTM) generally refers to a ranging protocol(e.g., as defined in the IEEE 802.11mc wireless standard) that measuresthe distance between two stations (STAs) by measuring round trip traveltime (RTT) of messages transmitted between an initiating STA and aresponding STA. FTM may have a ranging accuracy of around 3 meters. Asingle burst FTM measurement can be accomplished by exchanging 6 framesbetween the initiating STA and the responding STA.

FIG. 4 is an example call flow 400 illustrating a frame exchange for anexample FTM procedure. As shown in FIG. 4, the Initiating STA may sendan FTM Request (FTMR) frame to the Responding STA to start the FTMprocedure. As will be described in greater detail below, the FTMR mayinclude an indication of a resolution of units of time to use for one ormore parameters to be used in a ranging procedure performed with asecond apparatus (e.g., a wireless node).

The Responding STA may send an ACK to the Initiating STA. After the FTMRand ACK, the Responding STA may start sending FTM frames (with thetransmission times for the FTM frames indicated as t₁) which may bereceived by the Initiating STA at a time indicated as t₂. At t₃ theInitiating STA may respond with an ACK which may be received by theResponding STA at t₄.

As illustrated, these steps may be repeated for each FTM frame (FTM_1,FTM_2, FTM_3) transmitted by the Responding STA, for a total burstexchange of 6 FTM frames. In each case, the current FTM frame may havethe t₁ and the t₄ values from the previous FTM frame embedded (e.g.,FTM2 has the t₁ and the t₄ values from the FTM1 exchange). TheInitiating STA may then use t₁, t₂, t₃, and t₄ (since it already knowst2 and t3, having received an FTM at t2 and having sent an ACK at t3) toestimate the RTT between the Responding STA and the Initiating STA.

The RTT may be used estimate the range (distance) between the twowireless stations. To determine its own 2D location, one wirelessstation may acquire RTT measurements from at least three other wirelessstations that may have known 2D locations. The wireless station may usethe RTT measurements from the other wireless stations to compute its own2D location. This may increase the number of exchanged FTM frames andreduce network throughput.

FTM may be used as a way to measure range between two devices and may beincluded in physical layer (PHY) specifications of devices according tovarious versions of standards. Examples of such devices include devicescapable of high throughput (HT), very high throughput (VHT) and alsodirectional multigigabit (DMG) communications.

As used herein, the term DMG generally refers to operation in frequencybands with a starting frequency above 45 GHz. The term DMG may be usedin contrast to more frequency-specific terms LB (Low Band at 2.4 GHz),HB (High Band at 5 GHz), and UB (Ultra Band at 60 GHz). DMGcommunications may utilize, for example, a “60 GHz” band from 57 GHz to66 GHz.

Some of the principal parameters in certain versions of FTM may haveunit resolutions that are optimized for operation in certainfrequencies, such as 2.4 GHz and 5 GHz. Unfortunately, resolutionsoptimized for one frequency may not be optimal for another frequency. Asa result, devices capable of operating in different modes (frequencyranges) may suffer if they are limited to any fixed set of resolutions.

Aspects of the present disclosure, however, provide for signaling toindicate different resolutions for time units of various FTM parameters(contained in a frame) in a manner that may be backwards compatible. Forexample, such a mechanism may utilize a format of an existing messagestructure containint fields for FTM parameters, with a modification ofvarious parameters (e.g., using different resolutions) to enableoperation also in DMG mode.

In some cases, enabling FTM in devices capable of operating in a DMGmode may open up new options for FTM products. Such options may include,for example, fine range resolution (e.g., on the order of millimetersrather than meters). Further, enhanced throughput and reduced latency ofDMG may allow extensive FTM messaging and operation without efficiencyreduction. This may allow devices to achieve accurate results for FTMmeasurements, even when one or more of the devices involved are moving.

FIG. 5 illustrates a block diagram of example operations 500 forwireless communications by an apparatus, in accordance with certainaspects of the present disclosure.

The operations 500 may be performed, for example, by an initiating STA(e.g., the apparatus may be a user terminal 120 or other type wirelessstation). The operations 500 begin, at 502, by generating a first frameproviding an indication of a resolution of units of time to use for oneor more parameters to be used in a ranging procedure performed with awireless node. As illustrated in FIG. 4, in some cases, the indicationmay be provided in an FTM parameters field of an FTM request (FTMR)frame. At 504, the initiating STA may output the first frame fortransmission to the wireless node. The receiving apparatus, in somecases, may reject use of the indicated parametrs. If the receivingapparatus rejects in this manner, the initiating device may proposeother parameters. In some cases, the receiving apparatus may generate aframe confirming it accepts using the parameters indicated by theinitiateing apparatus.

FIG. 6 illustrates a block diagram of example operations 600 forwireless communications by a (different) apparatus, in accordance withcertain aspects of the present disclosure. The operations 600 may beconsidered complementary to the operations 500 of FIG. 5. In otherwords, operations 600 may be perfumed by a responding STA (e.g., anaccess point 110 or other type wireless station).

The operations 600 may begin, at 602, by obtaining a first frametransmitted from a wireless node. At 604, the responding STA maydetermine, based on an indication in the first frame, one or moreresolutions of units of time to use for one or more parameters to beused in a ranging procedure performed with the wireless node. At 606,the responding STA performs the ranging procedure according to thedetermined resolutions.

As noted above, in some cases, the indication of different resolutionsfor one of more FTM parameters may be provided. In some cases, theindication may be provided in an existing structure (e.g., using anexisting frame format).

For example, as shown in FIG. 7, a (previously) reserved bit B7 in anFTM parameters set field 700 may be used to indicate a “DMG mode” whereone or more FTM parameters use different resolution units (relative tothe resolution units used in a “non-DMG mode”). This may be advantageousin that such signaling may have no effect on ongoing Wi-Fi Alliance(WFA) Location certification (e.g., this bit is not required to be anycertain value).

In such cases, as illustrated in FIG. 8, setting this bit (e.g., B7=1)may indicate a change in resolution of one or more of the FTMparameters. For example, setting the bit may indicate that at least oneof at least one of a time of departure (TOD), time of arrival (TOA),maximum TOD error, or maximum TOA error may be expressed in time unitsof 1 ps, rather than 100 ps.

As another example, in DMG mode, the Min Delta FTM field (that indicatesa minimum time between consecutive FTM frames) may be expressed in unitsof 10 μs instead of 100 μs. As yet another example, in DMG mode, theburst period may be reported in units of 10 ms instead of 100 ms.

Depending on a particular embodiment, any combination of one or more ofthe above-mentioned parameters may have different resolutions. Further,in some cases, more than two sets of resolution units may be signaled(e.g., using more than a single bit).

In some cases, separate indications may be provided to indicatedifferent resolutions for different parameters (or different sets ofparameters). For example, one indication may be provided as discussedabove (B7=1), while a second indication may be provided via one or morebits of another existing field (e.g., FTM Format and Bandwidth). Thefirst indication may indicate different resolutions for a first set ofone or more parameters (e.g., TOD, TOA, maximum TOD error, or maximumTOA error), while the second indication may indicate differentresolutions for a second set of one or more parameters (e.g., a burstperiod or Min Delta FTM).

In cases where a multi-bit value is used to access a lookup table, theDMG mode bit may indicate one or more different values are used in thelookup table. For example, the burst duration values (e.g., in 802.11Table 8-246) may be set to 32 μs for entry 0 and 125 μs for entry 1.

As described herein, resolution of certain FTM parameters for DMG modemay be higher than for 2.4 and 5 GHz, due to the higher bandwidth (asresolution is generally inversely proportional to bandwidth). In somecases, FTM features may be implemented in hardware in DMG mode capabledevices (making it advantageous to use higher resolution). In suchcases, a packet exchange may include parameters to reduce the overalltime of FTM frame exchanges (such as SIFS=3 μs, Preambles=2.5 us, minpayload length=0.32 us, for a total delay for these parameters of2*3+2.5+0.32=8.7 μs).

In some cases, an FTM burst period may be limited to 100 ms, which maylimit the accuracy for cases with STA movement. However, using a 10 msburst duration instead of 100 ms burst duration may provide sufficientresolution, while maintaining low duty cycle. In some cases, a currentFTM minimum burst duration (e.g., 250 us) may correspond to 25 FTMmeasurements when done in DMG. Aspects of the present disclosure,however, may provide for shorter durations (e.g., higher accuracy usingrelatively fewer FTM measurements).

As noted, the techniques provided herein may allow for improvement inresolution to the FTM protocol, in a backward-compatible manner, thatmay help enable FTM operation in DMG PHY and allows for precisemeasurements (e.g., on the order of mm). The proposed changes may havelittle or no effect on existing (so called “legacy”) devices, nor on WFALocation certification of current FTM in 2.4 and 5 GHz bands. Thetechniques proposed herein may help align FTM to all bands defined inemerging standards, such as the IEEE 802.11REVmc specification. Thesuggested combination of DMG and FTM may give additional value to bothspecifications.

According to certain aspects, by applying the ranging techniquesdescribed above, devices may be able to achieve ranging results withhigher accuracy than previously possible. In addition, the results maybe achieved faster and, in some cases, with less overhead thantraditional techniques.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

In some cases, rather than actually transmitting a frame, a device mayhave an interface to output a frame for transmission. For example, aprocessor may output a frame, via a bus interface, to an RF front endfor transmission. Similarly, rather than actually receiving a frame, adevice may have an interface to obtain a frame received from anotherdevice. For example, a processor may obtain (or receive) a frame, via abus interface, from an RF front end for transmission.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering. For example, operations 500 and 600 illustrated inFIGS. 5 and 6 correspond to means 500A and 600A illustrated in FIGS. 5Aand 6A, respectively.

For example, means for receiving and means for obtaining may be areceiver (e.g., the receiver unit of transceiver 254) and/or anantenna(s) 252 of the user terminal 120 illustrated in FIG. 2 or thereceiver (e.g., the receiver unit of transceiver 222) and/or antenna(s)224 of access point 110 illustrated in FIG. 2. Means for transmittingand means for outputting may be a transmitter (e.g., the transmitterunit of transceiver 254) and/or an antenna(s) 252 of the user terminal120 illustrated in FIG. 2 or the transmitter (e.g., the transmitter unitof transceiver 222) and/or antenna(s) 224 of access point 110illustrated in FIG. 2.

Means for generating, means for performing, and means for determiningmay comprise a processing system, which may include one or moreprocessors, such as the RX data processor 270, the TX data processor288, and/or the controller 280 of the user terminal 120 illustrated inFIG. 2 or the TX data processor 210, RX data processor 242, and/or thecontroller 230 of the access point 110 illustrated in FIG. 2.

According to certain aspects, such means may be implemented byprocessing systems configured to perform the corresponding functions byimplementing various algorithms (e.g., in hardware or by executingsoftware instructions) described above. For example, an algorithm fordetermining a period that at least one second apparatus is scheduled tobe awake, an algorithm for generating a first frame for transmission tothe second apparatus during the period, an algorithm for outputting thefirst frame for transmission, an algorithm for obtaining a second framein response to the first frame, an algorithm for determining ranginginformation based on a time difference between transmission of the firstframe and receipt of the second frame, an algorithm for generate a thirdframe including the ranging information, and an algorithm for outputtingthe third frame for transmission. In another example, an algorithm fordetermining a period to awake from a low power state, an algorithm forobtaining a first frame from a second apparatus during the period, analgorithm for generating a second frame for transmission to the secondapparatus in response to the first frame, an algorithm for outputtingthe second frame for transmission to the second apparatus, an algorithmfor obtaining a third frame comprising ranging information, determinedby the second apparatus, based on a time difference between transmissionof the first frame and receipt of the second frame, and an algorithm fordetermining a relative location of the second apparatus to the apparatusbased on a third frame.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1), a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer-readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For example, instructions for determining a period that at leastone second apparatus is scheduled to be awake, instructions forgenerating a first frame for transmission to the second apparatus duringthe period, instructions for outputting the first frame fortransmission, instructions for obtaining a second frame in response tothe first frame, instructions for determining ranging information basedon a time difference between transmission of the first frame and receiptof the second frame, instructions for generate a third frame includingthe ranging information, and instructions for outputting the third framefor transmission. In another example, instructions for determining aperiod to awake from a low power state, instructions for obtaining afirst frame from a second apparatus during the period, instructions forgenerating a second frame for transmission to the second apparatus inresponse to the first frame, instructions for outputting the secondframe for transmission to the second apparatus, instructions forobtaining a third frame comprising ranging information, determined bythe second apparatus, based on a time difference between transmission ofthe first frame and receipt of the second frame, and instructions fordetermining a relative location of the second apparatus to the firstapparatus based on a third frame.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. An apparatus for wireless communications, comprising: a processing system configured to generate a first frame having at least one bit indicating one or more resolutions of units of time of a plurality of resolutions of units of time to use for one or more parameter fields to be used in a ranging procedure performed with a wireless node; and a first interface configured to output the first frame for transmission to the wireless node.
 2. The apparatus of claim 1, wherein the first frame comprises a trigger frame configured to initiate the ranging procedure.
 3. The apparatus of claim 2, wherein the trigger frame comprises a fine timing measurement (FTM) request trigger frame.
 4. The apparatus of claim 1, further comprising: a second interface to obtain one or more second frames during the ranging procedure, the one or more second frames comprising one or more parameters having values generated based on the one or more resolutions indicated by the at least one bit of the first frame.
 5. The apparatus of claim 4, wherein the processing system is further configured to determine a distance between the apparatus and the wireless node, based on the one or more parameter fields with values reported in the one or more resolutions indicated by the at least one bit of the first frame.
 6. The apparatus of claim 1, wherein: the at least one bit is part of a fine timing measurement (FTM) parameters element contained in the first frame.
 7. The apparatus of claim 1, further comprising: a second interface configured to obtain one or more second frames from the wireless node indicating the wireless node rejects use of the one or more resolutions indicated by the at least one bit in the first frame; and the processing system is configured to generate, after obtaining the one or more second frames, generate one or more third frames during the ranging procedure using one or more resolutions of units of time for the one or more parameter fields different than the one or more resolutions indicated in the first frame.
 8. The apparatus of claim 1, wherein: the one or more parameter fields comprise a parameter that indicates a minimum time between consecutive fine timing measurement (FTM) frames.
 9. The apparatus of claim 1, wherein the at least one bit comprises: a first one or more bits indicating a resolution of units of time to use for at least a first parameter to be used in the ranging procedure; and a second one or more bits indicating a resolution of units of time to use for at least a second parameter to be used in the ranging procedure.
 10. The apparatus of claim 9, wherein: the first parameter comprises at least one of a time of departure (TOD), time of arrival (TOA), maximum TOD error, or maximum TOA error.
 11. The apparatus of claim 9, wherein: the second parameter comprises at least one of a burst period or a parameter that indicates a minimum time between consecutive fine timing measurement (FTM) frames.
 12. The apparatus of claim 1, wherein: the one or more parameter fields comprise a parameter that indicates a burst period.
 13. An apparatus for wireless communications, comprising: a first interface configured to obtain a first frame transmitted from a wireless node; and a processing system configured to determine, based on at least one bit in the first frame, one or more resolutions of units of time of a plurality of resolutions of units of time to use for one or more parameter fields to be used in a ranging procedure and to perform the ranging procedure with the wireless node according to the determined one or more resolutions.
 14. The apparatus of claim 13, wherein: the first frame comprises a trigger frame to initiate the ranging procedure; the processing system is configured to generate, after obtaining the trigger frame, one or more second frames for the ranging procedure, the one or more second frames containing one or more parameters having values generated based on the determined one or more resolutions of units of time; and the apparatus further comprises a second interface to output the one or more second frames for transmission.
 15. The apparatus of claim 14, wherein the trigger frame comprises a fine timing measurement (FTM) request trigger frame.
 16. The apparatus of claim 13, wherein the processing system is configured to determine a distance between the apparatus and the wireless node, based on one or more parameters reported in the one or more resolutions by the wireless node.
 17. The apparatus of claim 13, wherein: the at least one bit comprises at least one bit of a fine timing measurement (FTM) parameters element of the first frame; and the processing system is configured to determine the one or more resolutions based on the at least one bit of the FTM parameters element.
 18. The apparatus of claim 13, wherein: the processing system is configured to generate a second frame with an indication that the apparatus accepts use of the one or more resolutions indicated in the first frame; and the apparatus further comprises a second interface configured to output the second frame for transmission.
 19. The apparatus of claim 13, wherein: the one or more parameter fields comprise a parameter that indicates a minimum time between consecutive fine timing measurement (FTM) frames.
 20. The apparatus of claim 13, wherein the at least one bit comprises: a first one or more bits providing an indication of a resolution of units of time to use for at least a first parameter to be used in the ranging procedure; and a second one or more bits providing an indication of a resolution of units of time to use for at least a second parameter to be used in the ranging procedure.
 21. The apparatus of claim 20, wherein: the first parameter comprises at least one of a time of departure (TOD), time of arrival (TOA), maximum TOD error, or maximum TOA error.
 22. The apparatus of claim 20, wherein: the second parameter comprises at least one of a burst period or a parameter that indicates a minimum time between consecutive fine timing measurement (FTM) frames.
 23. The apparatus of claim 13, wherein: the one or more parameter fields comprise a parameter indicating a burst period.
 24. A method for wireless communications by an apparatus, comprising: generating a first frame providing at least one bit indicating one or more resolutions of units of time of a plurality of resolutions of units of time to use for one or more parameter fields to be used in a ranging procedure performed with a wireless node; and outputting the first frame for transmission to the wireless node.
 25. The method of claim 24, wherein the first frame comprises a trigger frame configured to initiate the ranging procedure.
 26. The method of claim 25, wherein the trigger frame comprises a fine timing measurement (FTM) request trigger frame.
 27. The method of claim 24, further comprising: obtaining one or more second frames during the ranging procedure, the one or more second frames comprising one or more parameters having values generated based on the indicated resolutions of units of time indicated by the at least one bit of the first frame.
 28. The method of claim 27, further comprising determining a distance between the apparatus and the wireless node, based on the one or more parameters with values reported in the one or more resolution indicated by the at least one bit of the first frame.
 29. The method of claim 24, wherein: the at least one bit is part of a fine timing measurement (FTM) parameters element contained in the first frame.
 30. A method for wireless communications by an apparatus, comprising: obtaining a first frame transmitted from a wireless node; determining, based on at least one bit in the first frame, a resolution of units of time of a plurality of resolutions of units of time to use for one or more parameter fields to be used in a ranging procedure performed with the wireless node; and performing the ranging procedure with the wireless node according to the determined resolutions. 